1. Technical Field of the Invention
This invention relates to water treatment. The invention further relates to a method of treating water to decrease the concentration of pollutants dissolved in the water. The invention still further relates to a method of treating water to decrease the concentration of ammonia, chlorine, chloramines, nitrites and nitrates dissolved in the water. The invention particularly relates to a method of treating water with a water soluble, reducing agent comprised of a sulfur-containing organic compound to decrease the concentration of ammonia, chlorine, chloramines, nitrites and nitrates which are dissolved in the water.
2. Description of the Prior Art and Problems Solved
A field of art, referred to by some as aquaculture, broadly deals with plants and animals which live in water. It is known in that field of art that fish which live in water can be injured, if not killed, if the water environment in which the fish live becomes excessively polluted with certain dissolved material. Kuhns, in U.S. Pat. No. 4,666,610, discusses materials dissolved in water, and the danger posed by the dissolved materials to fish which live in the water. Kuhns variously refers to the dissolved material as toxins and pollutants. Kuhns addresses the danger under the broad headings of disease management and water quality management, and observes that disease management of fish is related to water quality. The background discussion provided by Kuhns is informative and is included herein by reference.
Materials dissolved in water which Kuhns specifically identifies as toxic to fish, when such materials are present in defined concentrations, are ammonia, chlorine and chloramines. According to Kuhns: Chlorine occurs in water in the form of hypochlorus acid (ClOH) and in ionic form as the hypochlorite ion (ClO—). Ammonia occurs in water as free ammonia (NH3) and in ionic form as the ammonium ion (+NH4), wherein ammonia is said to be more toxic than the ammonium ion. Chloramines, the reaction product of chlorine and ammonia, occurs in water as monochloramine and dichloramine.
It is believed that ammonia is present in natural waters as a direct result of the activity of the animals which live in the water (animal metabolism of proteins; urinary, fecal and respiratory wastes) and bacterial mineralization of nitrogenous bases. Accordingly, fish, and other aquatic organisms, contribute ammonia to their own water. In waste water, the previously mentioned animal sources, as well as technological wastes, account for the presence of ammonia. The presence of ammonia in potable water is believed to be due to the failure to remove it in the purification process or due to the purposeful addition for quality control.
The quantity of ammonia in water which, with respect to fish, is believed to be less than toxic level has been widely reported to be in the range of from about 0.005 to about 0.3 ppm (milligrams per liter of water). According to Kuhns, ammonia levels over 0.3 ppm are considered dangerous. One source states that short-term concentrations of ammonia should not exceed 0.1 mg/L and terms of about 4 days should be less than 0.02 mg/L.
Kuhns states that chlorine is not found in natural waters unless the natural water is mixed with wastewater or a potable water source. The presence of chlorine in water is said to be often caused because it is added to the water in an effort to disinfect municipal water supplies. In this regard, ammonia present in water can react with chlorine to form chloramines.
Kuhns argues that the concentration of chlorine must be reduced to zero before any water in which it is present can be safely used to house fish. He further states that chlorine concentration in the range of from 0.2 to 0.3 ppm is rapidly toxic to fish, and that the U.S. Environmental Protection Agency recommends an upper level of chlorine to be 0.003 ppm for continuous exposure to chlorine by cold water and warm water fishes. It would thus appear that the quantity of chlorine in water considered to be at a non-toxic level for fish is in the range of from about 0.000 to about 0.003 ppm (milligrams per liter of water).
Chloramine, like chlorine, is most often present in water because it is added in an effort to disinfect municipal water supplies. However, some chloramines in natural and waste waters result from the chemical combination of chlorine with the ammonia normally found in these waters. Kuhns states that municipal tap waters can contain chloramines in a concentration in the range of from 0.5 to 4.0 ppm which represents a deadly concentration level for aquatic life.
Kuhns discusses various types of systems for containing fish including the closed, recirculating system, such as a home aquarium, which is characterized by a fixed volume of water which is continuously or intermittently circulated through a fish holding tank. Kuhns maintains that the water environment of the closed, recirculating system can be controlled with intensive care and maintenance.
Kuhns states that the objective of successful water quality management is the removal or neutralization of toxic substances which stress cultured aquatic life forms, such as fish. Kuhns, thus, discloses the addition to the water of a material identified as an alkali metal formaldehydebisulfite, such as sodium formaldehydebisulfite, to remove or neutralize chlorine, chloramines and ammonia. According to Kuhns, the material is not toxic to fish and does not react with dissolved oxygen in either fresh waters or saline waters. Sodium formaldehydebisulfite is also known by other names including formaldehyde sodium bisulfite. The chemical structure of sodium formaldehydebisulfite is believed to be HO—CH2—SO3Na. The valence state of sulfur in sodium formaldehydebisulfite is believed to be +6.
The toxic nature of chlorine, ammonia and chloramines to fish, as above indicated, has been discussed by Kuhns. However, Kuhns does not discuss the toxic nature of nitrites and nitrates to fish. One author indicates that nitrates in drinking water have caused serious illness and death. The author states that nitrates can be converted to nitrites by action of the human body. The author further states that nitrates and nitrites are likely to remain in water until consumed by plants or other organisms. The author also states the existence of nitrate removal systems involving distillation, reverse osmosis and anion exchange.
Accordingly, there exists a general need for a chemical means of reducing the concentration of ammonia, chlorine, chloramines, nitrites and nitrates dissolved in water, and, more particularly, for reducing the concentration of ammonia, chlorine, chloramines, nitrites and nitrates dissolved water used to house fish.
It is thus an object of this invention to provide a chemical process for reducing the concentration of chloramines, chlorine, ammonia, nitrites and nitrates dissolved in fresh and saline water.